This invention relates in general to the manufacture and assembly of a vehicular exhaust system. More specifically, the invention relates to an improved structure and method for manufacturing a vehicular exhaust system using hydroforming and magnetic pulse welding techniques.
Virtually all vehicles, aircraft, and boats are powered by a fuel-burning engine and include an exhaust system that carries post combustion gaseous materials from the engine to a point removed from the passenger compartment. A typical basic exhaust system includes a metallic tube having a first end that is connected to an exhaust manifold provided on the engine and a second end extending outwardly from the lower rear end of the vehicle. Thus, the exhaust tube carries the post combustion gaseous materials from the engine to the exterior of the vehicle. Because of space constraints beneath the vehicle, such exhaust tubes are often bent at one or more locations to fit within the available space.
Frequently, these exhaust tubes include a structure for reducing the magnitude of the noise generated by the engine and for reducing the amount of post combustion products that are exhausted to the atmosphere, such as a muffler or a catalytic converter. A typical muffler or catalytic converter includes a pair of internal conduits that are supported by transversely extending baffles within a closed chamber. The chamber is usually formed from one or more sheets of metal that are stamped or otherwise deformed and secured together to provide a desired shape. The chamber normally has an inpening that is connected to a first tube-extending from the exhaust manifold to receive the post combustion products from the engine and an output opening that is connected to a second tube extending to a point removed from the passenger compartment. The physical arrangement of the baffles within the muffler chamber contributes to noise attenuation. Additionally, sound deadening materials and/or catalytic chemical materials may be provided within the chamber for reducing the magnitude of the noise generated by the engine and for reducing the amount of post combustion products that are exhausted to the atmosphere.
Known muffler designs generally involve a relatively large number of components that are assembled in a relatively labor intensive process. As mentioned above, the tubes are often bent in a plurality of locations. Furthermore, several of such tubes may be connected together by mechanical clamps or by welding. When weight is a consideration and the components are formed from aluminum or aluminum alloy materials, inert gas welding may be necessary to assure reliable welds. Also, sharp bends in the exhaust system are often created by welding relatively straight sections together. This creates sharp angles that may amplify sounds in certain frequency ranges. In addition, the chamber, as mentioned above, is frequently fabricated from plurality of stamped pieces or formed sheet metal. Assembly of such components requires welding seams and/or end pieces in addition to welding a variety of interior tubes. Generally, this results in additional labor intensive manufacturing steps. In addition, the parallel walls of such chambers and sharp comers decrease can noise attenuation and may create secondary noise.
As is well known, conventional welding techniques involve the application of heat to localized areas of two metallic members. This results in a coalescence of the two metallic members. Such welding may or may not be performed with the application of pressure, and may or may not include the use of a filler metal. Although conventional welding techniques have functioned satisfactorily in the past, there are some drawbacks in using them to join exhaust components together. First, as noted above, conventional welding techniques involve the application of heat to localized areas of the exhaust system. This application of heat can introduce undesirable distortions and weaknesses into the metallic components. Second, while conventional welding techniques are well suited for joining components that are formed from similar metallic materials, it has been found to be somewhat more difficult to adapt them for use in joining components formed from dissimilar metallic materials. Third, conventional welding techniques may not be easily adapted for joining components which have a different gauge thickness.
The production of vehicle exhaust systems is usually a high volume, low margin process and any improved structure and method of assembling a vehicle exhaust assembly would be advantageous. Thus, it would be desirable to provide an improved structure for a vehicle exhaust system and method of manufacturing same that is relatively simple and inexpensive.
This invention relates to an improved structure for a vehicle exhaust system and method for manufacturing same using hydroforming and magnetic impulse welding techniques. An exhaust system of the invention includes a flange adapted for connection to an exhaust manifold of an engine of a vehicle, a first exhaust tube having a first end connected to the flange and a second end expanded to form a first portion of a chamber, and a second exhaust tube having a first end expanded to form a second portion of a chamber closure and a second end open to atmosphere. The end portions of the first and second tubes may be formed to desired shapes using a hydroforming process. The second portion of the chamber is sized to fit inside the first portion of the chamber and can be secured thereto by magnetic pulse welding techniques. The exhaust system can further include a retainer tube that is connected to the first and second tubes by magnetic pulse welding techniques. A method of the invention for manufacturing a vehicle exhaust system includes the steps of pre-bending a first exhaust tube having a first end and a second end, pre-bending a second exhaust tube having a first end and a second end, hydroforming the second end of the first exhaust tube and the first end of the second exhaust tube to form an complementary shapes, and securing the ends of the exhaust tubes together using magnetic pulse weld techniques. The me d can also include the steps of securing a retainer tube to the first and second tube using magnetic pulse welding techniques.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.